Publications Repository - Helmholtz-Zentrum Dresden-Rossendorf

Bubble columns are widely applied reactors in the chemical process industry due to their excellent heat and mass transfer properties as well as their simple design and easy manufacturing without any moving part. Fischer-Tropsch and methanol syntheses are typical processes carried out in such columns. Most of the involved reactions are highly exothermic and require an efficient heat removal, for example, via internal tube bundle heat exchangers. Heat exchangers, with up to 60 m2 m-3 surface area, can be installed as dense tube bundles covering up to 60 % of the cross-sectional area, which accordingly, alter hydrodynamics, flow patterns, mixing and mass transfer significantly.
Therefore, this study aims at revealing the influence of common tube bundle layouts, i.e. triangular and square pitches, at various tube diameters at approx. 25 % cross-sectional area coverage. The studies were carried out using narrow and pilot-scale bubble columns with 100 and 400 mm diameter, respectively, operated with air and water. Ultrafast X-ray tomography as well as wire-mesh sensors were applied to study the columns’ hydrodynamics as well as the flow in individual sub-channels. In particular, holdup and bubble size distributions were measured and compared for both columns. Furthermore, it is discussed to which extend hydrodynamic parameters, such as radial holdup profiles and gas velocity profiles etc., can be utilized for scale-up purposes based on hydrodynamic similarity at both reactor scales.